Light signal



July 7, 1936. Q MEARA 2,046,906

LIGHT SIGNAL Filed Oct. 5, 1935 2 She-ts-Sheet 1 Y INVENTOR Thomas J. 0 Meara BY QRW HIS ATTORNEY July 7, 1936. T. J. OMEARA LIGHT SIGNAL Filed Oct. 5, 1933 2 Sheets-Sheet 2 IMVENTOR '7720mas J OMQG'PO' BY 2 W HIS ATTORNEY mama July 1, 1936 UNITED STATES PATENT OFFICE LIGHT SIGNAL Application October 3, 1933, Serial No. 691,967 4 (Cl. 176-26) My invention relates to light signals, and particularly to light signals for railway signaling purposes in which the source of light is an electric lamp. More particularly my present invention relates to screened double filament lamps for use in such signals, and has for an object the provision of an improved lamp of this type.

I will describe one form of lamp embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is an enlarged vertical sectional view showing one form of lamp embodying my invention. Fig. 2 is a sectional view of the lamp shown in Fig. 1 taken substantially on the line IIII of Fig. 1. Fig. 3

is a sectional view of the lamp shown in Fig. l

taken substantially on the line IIII]I of Fig. 1. Fig. 4 is a vertical sectional view illustrating the manner in which the lamp shown in Figs. 1, 2 2 and 3 is utilized in a lens type of light signal. Fig. 5 is a sectional view taken substantially on the line V-V of Fig. 4. Fig. 6 is a vertical sec- 1 tional view showing one manner in which the lamp illustrated in Figs. 1, 2 and 3 may be utilized in a railway signal of the Searchlight type. Fig. 7

is a sectional view of the reflector ll taken substantially on the line VIIVII of Fig. 6.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Figs. 1, 2 and 3, a lamp embodying my invention is here shown as comprising the usual evacuated glass bulb l secured to a base 2. The bulb I may have any desired shape or size, and the base 2 may be of any suitable type depending upon the type of socket in which the lamp is to be mounted. As shown in the drawings, the bulb is of the type known to the trade as Sl I, and the base is of the type known to the trade as a single contact bayonet candelabra.

Located within the bulb l is a main filament 3, an auxiliary filament 4 and a screen '5. The main filament 3 is of the concentrated type, and as here shown, is in the form of an inverted V. It is supported on the upper ends of a pair of lead-in wires 6 and 'l which extend upwardly through the usual glass stem 8, and is so positioned with respect to the base that when the lamp is properly positioned within a light signal, the filament will lie within the focal area of the optical system of the light signal. The filament 3 is further so positioned with respect to the base of the lamp that when the lamp is mounted vertically in a signal which projects a horizontal beam, the filament will lie in a plane which coin- 56 cides with the vertical axis of the lamp and which is normal to the optical axis of the signal.

The auxiliary filament 6 is also of the concentrated type and is preferably straight as shown.

It is supported at its upper end by a lead-in wire 9 which extends upwardly through the glass 5 stem 8, and at its lower end by an auxiliary wire Ill which is welded to the lead-in wire 6. The auxiliary filament extends parallel to the axis of the lamp in a plane which is normal to the plane of the main filament and which passes 10 through the vertical axis of the lamp. The auxiliary filament is located as close to the main filament as can conveniently be done from a manufacturing standpoint without causing any danger of short circuits and still permit the previl6 ously mentioned screen 5 to be disposed between the auxiliary filament and the main filament in the manner which I will now describe.

The screen 5 is secured to the lead-in wire 9, and as here shown is substantially L-shapecl in 20 cross section, although this particular shape is not essential. It is constructed of an opaque material having an outer surface which is preferably non-light reflecting, and is so positioned that its one leg 5' extends substantially parallel to the 25 plane of the main filament between the main filament and the auxiliary filament, and its other leg 5 extends away from the main filament past the auxiliary filament. The screen 5 is located as close to the auxiliary filament as is practical, and 30 the legs 5" and 5 are made just long enough so that when the auxiliary filament is lighted, the screen will shade practically all of the light emittedby this filament away from one-half of the lamp. 35

The lead-in wire 6 is electrically connected at its lower end to the base 2 of the lamp, while the lead-in wires 1 and 9 are each electrically connected at their lower ends to a base contact 2 which is insulated from the base 2 in the usual 40 manner. It will be apparent, therefore, that the main and auxiliary filaments are connected in multiple, so that when the lamp is put in use, both filaments will become lighted. The auxiliary filament is designed to have a higher voltage and :5 lower wattage rating than the main filament, and it follows that when the lamp is burned atthe rated voltage for the main filament, at which voltage it is intended to be burned, it is very probable that the main filament will burnout before 50 the auxiliary filament. When the main filament burns out, the auxiliary filament will remain lighted, but due to the screen 5, a portion of the lamp will be shaded. As a result, the lamp will continue to function, but due to the shaded portion and disposed in the path of the light rays.

' l8, as indicated by the dash lines I9.

also to the lower wattage rating of the auxiliary filament, an indication will be given that the main filament is burned out and that the lamp should be replaced.

Referring now to Figs. 4 and 5, I have here shown the lamp illustrated in Figs. 1, 2 and 3 incorporated in a light signal ll of the lens type, the lamp in the particular signal here shown being mounted vertically. It will be apparent from an inspection of the drawings that the lens I2 of the signal is entirely exposed to the light from the main filament 3 so that no light from this filament is lost due to the presence of the screen 5 in the lamp. It is also apparent that approximately one-half of the lens 12 is shaded from the auxiliary filament 4 by the screen 5 so that when the main filament 3 burns out, a portion of the lens I2 will appear brighter than the remaining portion, thus giving an indication that the main filament of the lamp is burned out without producing an entire signal failure.

In Figs. 6 and 7, I have shown my invention applied to a railway signal l6 of the searchlight type. As here illustrated, the signal lamp is mounted horizontally with its base 2 extending rearwardly through a suitable opening in an elliptical refiector II, the main filament 3 being located at the focal point of the reflector. The rays of light emitted by the lamp are collected by the reflector I I which causes them to converge at a focal point At the focal point, the rays pass through one of three differently colored roundels mounted in a spectacle arm 20 which is operated by relay mechanism not shown, to three different positions in each of which a diiferent one of the roundels is These roundels are usually colored green, yellow and red, respectively, and are so disposed in the spectacle arm that the red roundel is located between the green and yellow roundels, only the red roundel 2| being visible in the drawings. The rays of light after passing through one of the roundels diverge and pass through a lens 22 which causes them to emerge from the signal in a beam of substantially parallel rays.

With the signal constructed as just described, it will be noted that the spherical angle A of the elliptical reflector I! (see Fig. '7) is completely exposed to the light from the main filament .3; that the angles B and D are illuminated by direct light from one end or the other of the filament 3; and that the angle E is illuminated by both ends of the filament. It follows that no portion of the reflector is entirely shaded from the main filament.

It will also be noted that with the signal constructed in the manner just described, approximately one-half of the reflector is effectively shaded from the auxiliary filament 4 by the screen 5, so that in the event of the burning out of the main filament, a light and dark area will be produced in the lens 22.

I am aware that screened double filament lamps have been utilized for railway signals prior to my present invention, but in none of these lamps has the arrangement of the two filaments and the screen contemplated by my present invention been employed. One advantage of this arrangement is that it permits the main filament to be located at the focal point of the optical system in any of the existing types of light signals and at the same time retains all of the advantages to be gained by the use of a screened auxiliary filament, thus providing a more efllcient signal than has heretofore been possible with screened filament lamps.

Another advantage of the arrangement of the two filaments and the screen in a signal lamp in the manner contemplated by my present inven- 5 tion is that, as previously pointed out, the screen shades none of the light emitted by the main filament away from the lens in the usual type of lens signal or from the reflector in the usual type of reflector signal, and only a small amount of light from the reflector in a signal of the type wherein the axis of the lamp is parallel to or is on the axis of the reflector.

It should be particularly pointed out that while I have shown the screen 5 as being substantially 15 L-shaped in the drawings other shapes of screens may be employed with equally good results. For example, it is obvious that a semi-cylindrical screen could be used in place of the L-shaped screen. Likewise in some instances a straight fiat 20 screen interposed between the main and auxiliary filaments could be used, provided, of course, that this screen is located in the same position with respect to the two filaments of the lamp as the leg 5 of the screen 5 shown in the drawings is located 25 with respect to the filaments.

Although I have herein shown and described only one form of screened double filament lamp embodying my invention, it is understood that various changes and modifications may be made 0 therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. An electric signal lamp comprising an evacuated bulb provided with the usual glass stem and with a base, a first, a second and a third lead-in wire extending upwardly through said glass stem, said first lead-in wire being electrically connected at its lower end to said base and said second and third lead-in wires being electrically connected at their lower ends with a base contact which is insulated from said base, a main filament secured to the upper ends of said first and 5 second lead-in wires, said main filament being of the inverted V-shaped type and being disposed in a plane which passes through the longitudinal axis of the lamp, a straight auxiliary filament supported-at its upper end by said third lead-in wire and secured at its lower end to said first leadin wire by means of an auxiliary wire, said auxiliary filament being disposed in a plane which passes through the longitudinal axis of the lamp and which is normal to the plane of the main filament, and a screen secured to said third leadin wire and having a portion disposed between said two filaments and a portion extending away from said main filament past said auxiliary filament, the parts being so proportioned that said 60 screen shades approximately one-half of said bulb from the light emitted by said auxiliary filament, but only a small portion of the light emitted by said main filament from said bulb.

2. An electric signal lamp comprising an evac- 65 uated bulb provided with the usual glass stem and with a base, a first, a second and a third lead-in wire extending upwardly through said glass stem, said first lead-in wire being electrically connected at its lower ends to said base 70 and said second and third lead-in wires being electrically connected at their lower ends with a base contact which is insulated from said base,

a main filament secured to the upper ends of said first and second lead-in wires, said main filament 75 being of the inverted V-shaped type and bein disposed in a plane which passes through the longitudinal axis of the lamp, a straight auxiliary filament supported at its upper end by said third lead-in wire and secured at its lower end to said first lead-in wire by means of an auxiliary wire, said auxiliary filament being disposed in a plane which passes through the longitudinal axis of the lamp and which is normal to the plane of the main filament, and a screen of opaque material having a non-light reflecting outer surface, said screen being secured to said third leadin wire and having a portion disposed between said two filaments and a portion extending away from said main filament past said auxiliary filament, the parts being so proportioned that said screen shades approximately one-half of said bulb from the light emitted by said auxiliary filament, but only a small portion of said bulb from the light emitted by said auxiliary filament.

3. An electric signal lamp comprising an evacuated bulb provided with a base and with the usual glass stem, first, second, and third lead-in wires extending into said bulb through said stem, a main filament secured to said first and second lead-in wires, said main filament being disposed in a plane which includes the longitudinal axis of the lamp, an auxiliary filament secured to said first and third lead-in wires, said auxiliary filament being disposed in a plane which includes the longitudinal axis of the lamp and which is normal to the plane of the main filament, a screen supported by said third lead-in wire and having a portion disposed between said two filaments and a portion extending away from said main filament past said auxiliary filament, the parts being so proportioned that said screen shades approximately one-half of said bulb from the light emitted by said auxiliary filament, but that only a small part of the light emitted by said main fila- 5 ment is shaded from said bulb by said screen.

4. An electric signal lamp comprising an evacuated bulb provided with the usual glass stem and with a base, a first, a second and a third lead-in wire extending into said bulb through said stem, 10 said first lead-in wire being electrically connected at its lower end to said base and said second and third lead-in wires being electrically connected at their lower ends with a base contact which is to the plane of the main filament, and a screen supported by said third lead-in wire and having 5 a portion disposed between said two filaments and a portion extending away from said main filament past said auxiliary filament, the parts being so proportioned that said screen shades approximately one-half of said bulb from the light 0 emitted by said auxiliary filament, but that only a small part of the light emitted by said main filament is shaded from said bulb by said screen.

moms J. 0mm. 

